hibernate之HQL

一、hql语句基础知识

1. 什么是hql
HQL是Hibernate Query Language的缩写 hibernate查询语句

2. hql和sql区别/异同
HQL                                                                    　　         SQL
类名/属性                                                      　　　　       表名/列名
区分大小写,关键字不区分大小写                 　　　　　　不区分大小写
别名 　　　　　　　　　　　　　　　　　　　　　　　别名
?，从下标0开始计算位置(hibernate5之后不支持) 　　　  ?，从顺序1开始计算位置
:命名参数　　　　　　　　　　　　　　　　　　　　　不支持:命名参数
面向对象的查询语言　　　　　　　　　　　　　　　　 面向结构查询语言

3. 处理返回的结果集
3.1 查单个对象 返回一个对象 用的最多
　　select没有逗号
3.2 查询两个列段以上 返回Object[]
　　b.bookId, b.bookName
3.3 Map函数，不区分大小写 返回的是map集合
　　new Map(b.bookId as bid, b.bookName as bname)
3.4 查两个列段及以上，也可返回对象，前提是有对应的构造函数
　　new 构造方法(attr1,attr2)
　　new Book(b.bookId, b.price)
3.5查询单个列段 返回String

测试类HqlTest.java

package com.jt5.test;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.query.Query;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.jt2.util.SessionFactoryUtils;
import com.jt4.entity.Book;

public class HqlTest {
    private Session session;
    private Transaction transaction;
    
    @Before
    public void before() {
        session = SessionFactoryUtils.openSession();
        transaction = session.beginTransaction();
    }
    
    @After
    public void after() {
        transaction.commit();
        session.close();
    }
    
    /**
     * 返回对象（多个）
     */
    @Test
    public void testList1() {
        Query query = session.createQuery("from Book");
        List<Book> list = query.list();
        for (Book b : list) {
            System.out.println(b);
        }
    }
    
    /**
     * 返回单个列段，用字符串就可以接受
     */
    @Test
    public void testList2() {
        Query query = session.createQuery("select b.bookName as ss from Book b");
        List<String> list = query.list();
        for (String b : list) {
            System.out.println(b);
        }
    }
    
    /**
     * 查两个列段及以上，默认返回的是Object【】
     */
    @Test
    public void testList3() {
        Query query = session.createQuery("select b.bookId,b.bookName as ss from Book b");
        List<Object[]> list = query.list();
        for (Object[] b : list) {
            System.out.println(Arrays.toString(b));
        }
    }
    
    /**
     * 注意map是函数，所以不区分大小写，返回的是map集合
     * sum
     * count
     * 
     * 
     * 
     */
    @Test
    public void testList4() {
        Query query = session.createQuery("select new mAp(b.bookId,b.bookName) from Book b");
        List<Map> list = query.list();
        for (Map b : list) {
            System.out.println(b);
        }
    }
    
    /**
     * 查两个列段及以上，也可返回对象，前提是有对应的构造函数
     */
    @Test
    public void testList5() {
        Query query = session.createQuery("select new Book(b.bookId,b.bookName) from Book b");
        List<Book> list = query.list();
        for (Book b : list) {
            System.out.println(b);
        }
    }
    
    /**
     * HQL语句支持占位符
     */
    @Test
    public void testList6() {
//        Query query = session.createQuery("from Book where bookId = :bookId");
//        query.setParameter("bookId", 1);
//        Book b = (Book) query.getSingleResult();
//        System.out.println(b);
        
        Query query = session.createQuery("from Book where bookId in (:bookIds)");
        query.setParameterList("bookIds", new Integer[] {1,2,4});
//        List<Integer> params = new ArrayList<Integer>();
//        params.add(1);
//        params.add(2);
//        params.add(4);
//        query.setParameterList("bookIds", params);
        List<Book> list = query.list();
        for (Book b : list) {
            System.out.println(b);
        }
    }
    
    /**
     * HQL支持连接查询
     */
    @Test
    public void testList7() {
        Query query = session.createQuery("select o.orderNo,oi.quantity from Order o,OrderItem oi where o = oi.order");
        List<Object[]> list = query.list();
        for (Object[] b : list) {
            System.out.println(Arrays.toString(b));
        }
    }
    
    /**
     * HQL支持聚合函数
     */
    @Test
    public void testList8() {
        Query query = session.createQuery("select count(*) from Book");
        Long singleResult = (Long) query.getSingleResult();
        System.out.println(singleResult);
    }
    
    /**
     * sql=select * from t_hibernate_book
     * sql+ limit start,offset
     * 1       0,10
     * 2       10,10
     * 3        20,10
     * HQL分页
     */
    @Test
    public void testList9() {
        Query query = session.createQuery("from Book");
        query.setFirstResult(2);
        query.setMaxResults(3);
        List<Book> list = query.list();
        for (Book b : list) {
            System.out.println(b);
        }
    }
}

使用hql写一个分页查询

PageBean.java

package com.jt5.util;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;

/**
 * 分页工具类
 *
 */
public class PageBean {

    private int page = 1;// 页码

    private int rows = 3;// 页大小

    private int total = 0;// 总记录数

    private boolean pagination = true;// 是否分页
    // 获取前台向后台提交的所有参数
    private Map<String, String[]> parameterMap;
    // 获取上一次访问后台的url
    private String url;

    /**
     * 初始化pagebean
     * 
     * @param req
     */
    public void setRequest(HttpServletRequest req) {
        this.setPage(req.getParameter("page"));
        this.setRows(req.getParameter("rows"));
        // 只有jsp页面上填写pagination=false才是不分页
        this.setPagination(!"fasle".equals(req.getParameter("pagination")));
        this.setParameterMap(req.getParameterMap());
        this.setUrl(req.getRequestURL().toString());
    }

    public int getMaxPage() {
        return this.total % this.rows == 0 ? this.total / this.rows : this.total / this.rows + 1;
    }

    public int nextPage() {
        return this.page < this.getMaxPage() ? this.page + 1 : this.getMaxPage();
    }

    public int previousPage() {
        return this.page > 1 ? this.page - 1 : 1;
    }

    public PageBean() {
        super();
    }

    public int getPage() {
        return page;
    }

    public void setPage(int page) {
        this.page = page;
    }

    public void setPage(String page) {
        this.page = StringUtils.isBlank(page) ? this.page : Integer.valueOf(page);
    }

    public int getRows() {
        return rows;
    }

    public void setRows(int rows) {
        this.rows = rows;
    }

    public void setRows(String rows) {
        this.rows = StringUtils.isBlank(rows) ? this.rows : Integer.valueOf(rows);
    }

    public int getTotal() {
        return total;
    }

    public void setTotal(int total) {
        this.total = total;
    }

    public void setTotal(String total) {
        this.total = Integer.parseInt(total);
    }

    public boolean isPagination() {
        return pagination;
    }

    public void setPagination(boolean pagination) {
        this.pagination = pagination;
    }

    public Map<String, String[]> getParameterMap() {
        return parameterMap;
    }

    public void setParameterMap(Map<String, String[]> parameterMap) {
        this.parameterMap = parameterMap;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    /**
     * 获得起始记录的下标
     * 
     * @return
     */
    public int getStartIndex() {
        return (this.page - 1) * this.rows;
    }

    @Override
    public String toString() {
        return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination
                + ", parameterMap=" + parameterMap + ", url=" + url + "]";
    }

}

StringUtils.java

package com.jt5.util;

public class StringUtils {
    // 私有的构造方法，保护此类不能在外部实例化
    private StringUtils() {
    }

    /**
     * 如果字符串等于null或去空格后等于""，则返回true，否则返回false
     * 
     * @param s
     * @return
     */
    public static boolean isBlank(String s) {
        boolean b = false;
        if (null == s || s.trim().equals("")) {
            b = true;
        }
        return b;
    }
    
    /**
     * 如果字符串不等于null或去空格后不等于""，则返回true，否则返回false
     * 
     * @param s
     * @return
     */
    public static boolean isNotBlank(String s) {
        return !isBlank(s);
    }

}

记下来看看dao方法首先我们要写一个BaseDao.java

package com.jt5.util;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.query.Query;


/**
 * hebernate的通用查询Dao层
 * 思想完全借鉴于sql的BaseDao
 *  sql=select * from t_mvc_book where bname like '%圣墟%'
 *  countsql=select count(1) from (sql) t;
 *  pagesql=sql limit start,offset
 *  
 *  hql:
 *   hql=selct * from Book where bookName like :bookName
 *   hql=from Book where bookName like :bookName
 *    思想：原生的hql语句以from关键字进行截取
 *     countHql=select count(*) from Book where bookName like :bookName;
 *     pageHql不需要写：应为Hibernate已经封装了内置的分页接口
 *         getFirstResult
 *         getMaxResult
 * @author jt
 *
 */
public class BaseDao {

    /**
     * 给hiberbate中Query对象中的命名参数列表赋值
     * @param query
     * @param map
     */
    public void setparam(Query query,Map<String, Object> map) {
        if(map!=null && map.size()>0) {
            Set<Entry<String,Object>> entrySet = map.entrySet();
            
            for (Entry<String, Object> entry : entrySet) {
                Object value = entry.getValue();
                if(value instanceof Collection) 
                    query.setParameterList(entry.getKey(), (Collection)value);
                    else if(value instanceof Object[]) 
                        
                    
                    query.setParameterList(entry.getKey(), (Object[])value);
                    else
                    query.setParameter(entry.getKey(), value);    
                
                
            
        }
        
        
    }
    }
    
    /**
     *  hql:
     * hql=select * from Book where  bookName like :bookName
     * hql=from Book where bookName like :bookName
     * 思想：将原生态的hql语句以from关键字进行截取
     * counthql =select count(*) from Book where bookName like :bookName;
     * @param hql
     * @return
     */
    public String getCountHql(String hql) {
        return "select count(*)"+ hql.substring(hql.toUpperCase().indexOf("FROM"));
    }
    
    /**
     * 通用hql语句查询
     * @param session  当前会话
     * @param hql        带命名参数的hql语句
     * @param map        命名参数对应的值的集合
     * @param pageBean    分页实体类
     * @return
     */
    public List executeQuery(Session session,String hql,Map<String, Object> map,PageBean pageBean) {
        List list=null;
        Query query=null;
        if(pageBean!=null&&pageBean.isPagination()) {
            String countHql = getCountHql(hql);
            Query createQuery = session.createQuery(countHql);
            this.setparam(createQuery, map);
            pageBean.setTotal(createQuery.getSingleResult().toString());
             query = session.createQuery(hql);
                this.setparam(query, map);
                query.setFirstResult(pageBean.getStartIndex());
                query.setMaxResults(pageBean.getRows());
                list=query.list();
        }else {
             query = session.createQuery(hql);
                this.setparam(query, map);
            list=query.list();
        }
        return list;
    }
    
    
    
    }

然后再是BookDao.java

package com.jt4.dao;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.query.Query;

import com.jt2.util.SessionFactoryUtils;
import com.jt4.entity.Book;
import com.jt4.entity.Category;
import com.jt5.util.BaseDao;
import com.jt5.util.PageBean;
import com.jt5.util.StringUtils;

public class BookDao extends BaseDao{
    public Integer addBook(Book book) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Integer bid = (Integer) session.save(book);
        transaction.commit();
        session.close();
        return bid;
    }
    
    public Integer addCategory(Category category) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Integer cid = (Integer) session.save(category);
        transaction.commit();
        session.close();
        return cid;
    }
    
    public Category getCategory(Category category) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Category c = session.get(Category.class, category.getCategoryId());
        transaction.commit();
        session.close();
        return c;
    }
    
    public Book getBook(Book book) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Book b = session.get(Book.class, book.getBookId());
        if (b != null && new Integer(1).equals(book.getInitCategories())) {
            Hibernate.initialize(b.getCategories());
        }
        transaction.commit();
        session.close();
        return b;
    }
    
    public void delBook(Book book) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        session.delete(book);
        transaction.commit();
        session.close();
    }
    
    public void delCategory(Category category) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Category c = session.get(Category.class, category.getCategoryId());
        if(c!=null) {
            for (Book b : c.getBooks()) {
//                通过在被控方通过主控方来解除关联关系，最后被控方再做删除
                b.getCategories().remove(c);
            }
        }
        session.delete(c);
        transaction.commit();
        session.close();
    }
    /**********************************************/
     
    public List<Book> list1(Book book,PageBean pageBean) {
        Session session=SessionFactoryUtils.openSession();
        Transaction transaction=session.beginTransaction();
        //下面代码处理的是book实体类的条件查询 10*2
        String bookName=book.getBookName();
        //sql语句where后面可以直接写true，而hql与不能出现true
        String hql="from Book where 1=1";
        if(StringUtils.isNotBlank(bookName)) {
            hql+=" and bookName like :bookName";
        }
        Query query = session.createQuery(hql);
        if(StringUtils.isNotBlank(bookName)) {
            query.setParameter("bookName",bookName);
        }
        //处理的是分页
        if(pageBean!=null&&pageBean.isPagination()) {
            query.setFirstResult(pageBean.getStartIndex());
            query.setMaxResults(pageBean.getRows());
        }
        List list=query.list();
        transaction.commit();
        session.close();
        return list;
    }
    
    public List<Book> list2(Book book,PageBean pageBean) {
        Session session=SessionFactoryUtils.openSession();
        Transaction transaction=session.beginTransaction();
        //下面代码处理的是book实体类的条件查询 10*2
        String bookName=book.getBookName();
        Map<String,Object> map=new HashMap<String,Object>();
        //sql语句where后面可以直接写true，而hql与不能出现true
        String hql="from Book where 1=1";
        if(StringUtils.isNotBlank(bookName)) {
            hql+=" and bookName like :bookName";
            
            map.put("bookName",bookName);
        }
        List list=super.executeQuery(session, hql, map, pageBean);
        transaction.commit();
        session.close();
        return list;
    }
    
}

接下来是测试类BookDaoTest.java

package com.jt4.dao;

import java.util.List;

import org.junit.Test;

import com.jt4.entity.Book;
import com.jt4.entity.Category;
import com.jt5.util.PageBean;

public class BookDaoTest {
    private BookDao bookDao = new BookDao();

    @Test
    public void testGetBook() {
        Book book = new Book();
        book.setBookId(8);
        book.setInitCategories(1);
        Book b = this.bookDao.getBook(book );
        System.out.println(b.getBookName());
        System.out.println(b.getCategories());
    }
    
    /**
     * book.hbm.xml    inverse=fasle
     * category.hbm.xml inverse=true
     * 数据添加正常
     * 书籍表、桥接表各新增一条数据
     */
    @Test
    public void test1() {
        Book book = new Book();
        book.setBookName("jt66666666");
        book.setPrice(10f);
        Category category = new Category();
        category.setCategoryId(5);
//        直接将category对象加入到新建的book中是错误的，因为此时的category是临时态的，hibernate是不会管理的
//        book.getCategories().add(category);
        Category c = this.bookDao.getCategory(category);
        
//        c.getBooks().add(book);
        book.getCategories().add(c);
        this.bookDao.addBook(book);
    }

    /**
     * book.hbm.xml    inverse=false
     * category.hbm.xml inverse=true
     * 只增加书籍表数据
     * 桥接表不加数据
     * 原因：双方都没有去维护关系
     */
    @Test
    public void test2() {
        Book book = new Book();
        book.setBookName("jt555555");
        book.setPrice(10f);
        Category category = new Category();
        category.setCategoryId(5);
        Category c = this.bookDao.getCategory(category);
        
        book.getCategories().add(c);
        this.bookDao.addBook(book);
//        c.getBooks().add(book);
    }
    @Test
    public void testlist1() {
        Book book=new Book();
    book.setBookName("%jt%");
        
        PageBean pageBean=new PageBean();
        //pageBean.setPage(2);
        List<Book> list1 = this.bookDao.list1(book, pageBean);
        for (Book b : list1) {
            System.out.println(b);
            
        }
    }
    
    @Test
    public void testList2() {
        Book book=new Book();
//        book.setBookName("%jt%");
        PageBean pageBean=new PageBean();
        pageBean.setPage(2);
        List<Book> list2 = this.bookDao.list2(book, null);
        for (Book b : list2) {
            System.out.println(b);
        }
    }
    
}